tetramethylsilicon

Tetramethylsilicon, often abbreviated as TMS, is an organosilicon compound with the chemical formula Si(CH₃)₄. It is a colorless liquid that is volatile and flammable. TMS is notable for its role as a reference standard in nuclear magnetic resonance (NMR) spectroscopy. In ¹H NMR spectroscopy, TMS is assigned a chemical shift of 0 parts per million (ppm) due to the high electron density around the hydrogen atoms in its methyl groups. This high electron density shields the protons from the external magnetic field, causing them to resonate at a lower frequency compared to most other organic compounds. Therefore, other signals in an NMR spectrum are measured relative to TMS. Its inertness and volatility are key properties that make it suitable for this purpose. It does not react with most common NMR solvents and can be easily removed from the sample after the spectrum is recorded. TMS is also used as a calibrant in ¹³C NMR spectroscopy, where the quaternary carbon atom is assigned a chemical shift of 0 ppm. Beyond its spectroscopic applications, TMS is also used as a building block in the synthesis of silicon-containing polymers and other specialty chemicals. It can be prepared through the reaction of silicon tetrachloride with methylmagnesium bromide, a Grignard reagent.